1. What would be the consequence of a comet’s tail sweeping across Earth? 2. Project what human civilization would be like if Earth had no Moon. 3. What are the chances that microbial life forms might...

1. What would be the consequence of a comet’s tail sweeping across Earth?

2. Project what human civilization would be like if Earth had no Moon.

3. What are the chances that microbial life forms might one day be found elsewhere in our solar system? How much effort should we spend on searching for such life forms, and what precautions should we take upon such a discovery?